Install a Ceiling Light and Switch

Got light where you need it? Probably not. No house seems to have exactly the right lights, in the right place, with convenient, safe switches. Even if a plug-in hanging lamp is where you want it, built-in wiring is safer, more convenient, and easier on the eyes. And it can, as in our example, be fitted with a dimmer switch.

In this improvement, we'll look at some basic electrical techniques, and then add a light near an electrical outlet. The hard part about running cable is getting through walls without destroying them; always try to run cable through an unfinished area, like a basement, attic, or garage.

Running cable through finished walls can be frustrating. Wires get stuck. The fish tape you use to pull wires through the wall gets stuck. Be creative. Visualize where the fish tape is going, and why it's hung up.

Basic Electrical Jargon and Safety

Working with electricity is not tricky, but it can be dangerous. If you are inexperienced or uncertain of what you are doing, consult a more thorough treatment, such as the chapter on electricity in The Complete Idiot's Guide to Home Repair and Maintenance Illustrated. The following jargon and basic rules will help keep you out of trouble:

• Hot wires (usually black, sometimes red) carry incoming electricity.

• Ground (white, often called neutral) wires take electricity back to the utility.

• Equipment grounding conductors (usually bare copper, sometimes green) are a safety system that allows electricity to return if something goes wrong.

• Supply wires enter a box and bring electrical current.

• Current is the flow of electricity.

What size box do you need? To prevent overheating, the National Electric Code restricts how much junk you can jam into a box. The capacity, in cubic inches, should be marked on each box. Here's how to calculate the box size needed:

Each hot and neutral wire	1
All ground wires	1
Each switch and receptacle	2
All wire clamps	1
Add:	+ ______
Total:

Multiply by 2 (for 14-gauge wire) or 2.25 (for 12-gauge wire). Result: minimum box volume required, in cubic inches.

Here are some electrical do's and don'ts:

• Do test your circuit tester, an essential tool that detects electricity when connected between hot and ground, in a working outlet. Don't trust—verify that the tester will protect you from live electricity.

• Don't use undersize wire or fixtures (lights or outlets). Most lights are wired with 14-gauge wire (connected to 15-amp fuses or circuit breakers). 12-gauge wires should be protected by 20-amp fuses or breakers. Read the breaker or fuse, and choose your wire accordingly. If you can't tell the difference, it's usually safe to use 12-gauge wire.

• Do shut off circuits before you work on them. Then test that the circuit is cold using a circuit tester.

• Don't fool around with aluminum wire, used in some houses built in the 1960s and 1970s. Aluminum is silvery-gray, whereas the more common and much safer copper is dull brown. Connecting to aluminum is tricky; it's smart to hire a qualified electrician to work on aluminum.

• Do make all connections inside boxes. Leave all boxes accessible and do not hide an electrical box behind a wall.

• Don't fool with electrical boxes containing a dense snarl of wires. These boxes, often found in a basement or near the circuit-breaker panel, may be powered by two separate circuits, and it's hard to be sure the power is off. Call an electrician.

• Don't get in over your head. Any time you are thoroughly confused, it's time to call in a professional electrician.

Step 1: Locate the Force

First find a source of power for the new light. An existing outlet is the most common source, but a switch is another possibility, if both the black and white wires are in the box. Also check for an electrical box—a metal or plastic box holding electrical connections—on the basement ceiling.

Once you have located the source box, follow these steps:

1. Shut off the circuit you think feeds the box. Test between each pair of holes in the outlet. If the tester is working, and it never lights, the circuit is cold, and safe to work on.

2. Remove the two mounting screws and pull out the old outlet.

On old wiring, it can be hard to distinguish the black wire. Here's how to tell:

1. Disconnect the wires from the outlet and keep them separate from each other.

2. Turn the circuit back on. Plug a grounded extension cord in a grounded outlet. Make sure your circuit tester lights when you touch the round hole and the small slot in the extension cord.

3. Bring the cord to the supply box. Hold one end of the tester in the round hole and touch the wires with the other end until you find the hot wire. Remember its location.

4. Switch off the circuit breaker or fuse. Now mark the hot wire, which will supply both the old outlet and the new light. Also mark other black wires that are connected in this box.

Step 2: Cut Box Holes

After ensuring that you have an accessible supply of electricity, follow these steps:

1. Locate the switch and light boxes. If possible, plan to fasten boxes to studs or joists (the ceiling beams). Find the studs and joists, which are usually 16" apart, by tapping on the wall or ceiling. Drill a small hole to confirm the location; the drill bit should hit wood in the stud or joist.

2. Cut access holes in the upper wall and ceiling, about 5" square, avoiding the framing. Square or rectangular holes are easier to patch. Likewise, separate holes, as already shown, are easier to repair than one big hole that meets at the ceiling corner.

3. Locate the light box. Generally, octagonal boxes are used for ceiling lights. Hold the box against the ceiling, mark the opening, and then cut.

To mount a light in the ceiling, and connect it to a wall switch, I cut four holes: one each for the switch and light boxes, and two for routing cable. Think of these as fishing holes.

Measure the height of an electrical switch in the room. Place the bottom of the new box at the same height. Using a level, mark the new switch box cutout on the wall. (If you can't mount the box alongside a stud, buy a box designed to grab drywall; these are convenient but weaker.)

To start the saw blade, drill a ³⁄₈" hole at each corner. Also drill for the switch-mounting screws at center top and bottom.

A jigsaw makes a fine instrument for cutting a box opening in plaster or drywall. Run a variable-speed jigsaw slowly to control dust. An extra-short blade will preserve cables already in the wall.

Step 3: Fishing the Wire Through the Wall

With the box holes cut, turn your attention to electrical cable. If you are working on a 15-amp circuit (check the fuse or circuit breaker), use 14-gauge wire. Use 12-gauge wire for a 20-amp circuit. First drill holes to run the cable, and then pull cable between the box openings.

Drilling for Cable

Extra-long drill bits are essential for drilling these holes, and I advise using an 18"-long bit, ³⁄₄" in diameter from the start. In the example, you will drill only one hole, up through the plate, the framing on top of the studs, at a steep angle. In other situations, you might have to drill sideways through studs; the technique is similar to what's shown here.

Fishing for Cable

It's finally time to fish cables. One cable runs from the outlet to the switch box. The second cable runs between the switch and light boxes.

1. Uncoil a few feet of fish tape and work it down from the switch hole to the outlet.

2. Connect the cable to the fish tape and pull it up to the switch box hole.

   Use electrical tape to attach cable to the fish tape, a springy steel tape that pulls cable through walls. Extra hands are helpful: One person pushes cable into one hole, while the other pulls the fish tape from the other hole. Leave 15" of cable sticking out of each opening.

3. Push the fish tape down from the upper wall hole to the switch hole. Pull the cable up to the upper hole.

4. Run the tape down from the ceiling hole through the plate, to the upper wall hole, attach the cable, and pull it back to the ceiling hole.

5. Finally, push the cable into the light box hole. Cut off all cables, leaving 15" sticking out of the openings.

Step 4: Mount the Boxes

The hard work is now done, even though your place looks like the aftermath of Hurricane Fishtape. Take heart, things can only get easier from here.

A long drill bit will reach into the box as you prepare to screw it to a joist. Similarly, a long screwdriver bit is best for driving the mounting screws. Mount the box flush to the ceiling.

Handy boxes with sloped shoulders are much easier than rectangular boxes because the cables won't snag on the plaster as you push the box into the opening.

Step 5: Repair the Damage

Once the cable is run and the boxes are attached, it's time to repair the damage, using a three-step process: 1) fasten backer boards across the opening; 2) screw scraps of drywall to the backers, and 3) finish the patch with joint compound.

Drill holes to reduce wall damage, and then screw through the wall to attach wood backer strips (roughly 1 ¹⁄₂" × 8").

Cut patches made of drywall and gently screw them to the backers. You may need shims (of cardboard, plywood, drywall, or roof shingle) so the drywall is flush to, or slightly below, the surface.

Screw the drywall patch to the backer without loosening the backer.

With the patch in place, apply drywall tape and trowel on a quick-setting compound. This stuff fills deep holes better than drywall joint compound, and then sets faster.

Shift to normal joint compound after the quick-setting compound. Let the joint compound dry, sand lightly, and then put on a finish coat to match your wall.

Step 6: Connecting the Fixtures

Finally it's time to make the electrical connections. Consult the following directions for some general information on electrical connections. Then read how to connect the three boxes in this lighting setup.

Making Electrical Connections

To wire a box, follow these steps:

1. Tighten the cable clamps (found only in metal boxes). You'll see two types of clamp; metal boxes may use one or both types. Tighten the two screws evenly, and then insert the cable clamp into a round hole in a metal box. Turn the big ring to clamp the clamp to the box.

2. Remove the cable sheath. A utility knife will strip the outer sheath from cable. Don't cut the wires inside.

3. Strip ³⁄₄" of insulation from the wire ends. A wire stripper removes insulation from the black and white wires. These nifty strippers will also strip the sheath.

4. Connect wires together: To join wires to each other, use screw-on connectors, sold in various sizes for various combinations of wires.

5. Connect wires to fixtures: The basic rule is that black wire goes to brass screws; white wire goes to silver-colored screws. Some electrical fixtures use slip-in connectors (round holes on the back in which you stick a stripped wire end). I prefer screw terminals. Screw terminals, not the slip-in connectors, give a better connection to a receptacle. Strip the wire, make a hook, close the hook over the screw, and tighten.

6. Ground connections: The equipment grounding system should connect all bare wires, all metal boxes, and the metal body of every fixture. Grounding screws or clips connect the ground system to metal boxes. Screw the grounding screw into a threaded hole in the back of the box. No threaded hole? Use a grounding clip, sold in the same section of the building-material store.

Dim Wits

Now that we've seen how to make basic electrical connections, it's time to actually make some connections. We'll start wiring boxes at the dimmer switch, using screw-on connectors.

Connect the white wires from each cable. Attach one black wire on the dimmer to a black wire coming from the outlet. Connect the other black wire to the black wire going to the light.

To ground the dimmer box, connect both bare wires. If the box is metal, these wires also should connect to a short bare wire going to a ground screw or clip on the box.

Now screw the dimmer switch to the box.

Rewire the Outlet

With the dimmer in place, let's get some power to the dimmer. Don't be tempted to connect all wires to screws of the receptacle. Instead, connect the wires to short wire “pigtails,” which are then connected to the receptacle.

With the receptacle connected, screw it in place and test it. A circuit tester must light between the short (hot) slot and a) the long (grounded) slot, and b) the round (equipment grounding) hole. The tester must not light between the long slot and the round hole!

This Light Is Lit

Finally we move to the last box—the one holding the light. First connect the wires.

The final steps in the process are easy:

1. Follow the instructions for mounting the light fixture.

2. Screw face plates on the receptacle and light switch.

3. Turn the circuit back on and make sure the switch operates the light.

4. Touch the circuit tester to the light body and the round hole of a grounded extension cord. If the light lights, you have made a serious wiring mistake—turn the circuit off and check that black goes to black, and white to white.

5. If the tester does not light, congratulations. You are finished!

Excerpted from The Complete Idiot's Guide to Simple Home Improvements © 2004 by David J. Tenenbaum. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

To order this book visit Amazon or call 1-800-253-6476.